\begin{tikzpicture}
    \tkzDefPoints{0/0/B, 4/0/C}
    \tkzDefPointOnCircle[R = center B angle 44  radius 3] \tkzGetPoint{a1}
    \tkzDefPointOnCircle[R = center C angle 123 radius 3] \tkzGetPoint{a2}
    \tkzInterLL(B,a1)(C,a2)  \tkzGetPoint{A}

    \tkzDefLine[parallel=through A](B,C) \tkzGetPoint{d}
    \tkzDefPointBy[projection= onto A--d](C)  \tkzGetPoint{E}
    \tkzDefPointBy[projection= onto A--d](B)  \tkzGetPoint{D}

    \tkzDrawPolygon(A,B,C)
    \tkzDrawSegments(D,E)
    \tkzLabelPoints[above](A)
    \tkzLabelPoints[below](D,E)
    \tkzLabelPoints[left](B)
    \tkzLabelPoints[right](C)
\end{tikzpicture}

